I guess if you only use reduced loads than you could rechamber in 30-378WBY too. But what would be the point.
The pressure reduction with TSX bullets is negligible and there are other factors involved when determining which cartridges may be safely be handled by the Encore. Total breech face thrust is one of them.
Personally, I wouldn't want to rechamber an Encore for any cartridge that T/C does not. However, for a definitive answer, contact T/C.